1. Field Of The Invention
The present invention relates to fuel injection nozzles and in particular to such an injection nozzle device and a method for making the same wherein the nozzle spray hole temperature is maintained at a reduced level during operation to prevent coking.
2. Description Of The Prior Art
It is known that the tips of injection nozzles for internal combustion engines, particularly those for direct-injection internal combustion engines, should not become hotter than approximately 220.degree. C. when a gas or oil is employed as a fuel. When such temperature is exceeded, the spray holes often become closed due to coking of the fuel, so that the amount of fuel supplied to the combustion chamber is diminished and an orderly combustion process can thus not be achieved. In order to prevent the spray holes from being closed because of such buildup of coke, the injection nozzles have in the past been provided with water cooling. This can be accomplished in large diesel engines, but it is virtually impossible to do in vehicle engines due to their relatively small nozzle size and small combustion chambers. Also, such water cooling dictates the use of water as a general cooling agent for the internal combustion engine since the installation of a separate coolant circulating circuit solely for the injection nozzles would involve prohibitive costs.